A rotating electric machine such as a motor and a generator mounted on a vehicle for use includes a rotor, and a stator having a stator core with a plurality of slots and a stator winding wound through the slots. The stator winding is wound in a form of phase windings along the circumferential direction of the stator core, and the phase windings are arranged in the radial direction of the stator core, that is from the inner side to the outer side.
Each stator winding is formed by inserting ends of conductor segments formed in a substantially U-shape into the slots from a first end face of the stator core in the axial direction, and joining the ends drawn out from the slots on at second end face of the stator core by TIG welding, for example.
When the ends of the conductor segments are joined by TIG welding, the joint parts are formed in drop-like shape by the molten metal for welding. The drop-like joint parts have large conductor diameters, which may cause short-circuit of portions of the stator winding adjacent in the radial direction of the stator core.
Thus, a method of joining the ends of conductor segments by laser welding has been employed. In laser welding, a recess is formed on one side face of each conductor segment, the conductor segments are subjected to laser irradiation in a state in which the recesses face each other, so that joint surfaces are welded (for example, refer to PTL 1). It is mentioned that, with this method, since a joint part is formed on the side of conductor segments facing each other, portions of the stator winding neighboring in the radial direction of the stator core are prevented from short-circuiting.